title: External quality control of cervical cytopathology: interlaboratory variability.
abstract: OBJECTIVE
  To compare the variability of screening tests held at laboratories with the Unit for External Quality Control (UEQC), checking the frequency of cases that were discordant, false-positive, false-negative, unsatisfactory or that had a delay in clinical management and diagnostic agreement.
  
  
  METHODS
  The study analyzed 10,053 screening tests from January 2007 to December 2008, including all positive cases, all those that fall under unsatisfactory and at least 10% of negative screening tests. The magnitude of the agreement was analyzed using the kappa coefficient.
  
  
  RESULTS
  Out of the 10,053 cases analyzed, 7.59% were considered disagreeing, and it was estimated that 1.1% were false-negative. There was a delay in the clinical procedure regarding 2.44% cases. There were 2.82% of cases identified as false-positive and 1.24% as unsatisfactory. The diagnostic agreement was excellent (kappa = 0.81). The agreement of most laboratories concerning screening tests was classified as very good. The agreement of the sample adequacy was reasonable (kappa = 0.30) and the agreement regarding the representation of epithelia was considered excellent.
  
  
  CONCLUSIONS
  Most laboratories showed very good agreement; however, it is worthy of note that to establish the standardization of diagnostic criteria, and enhance the accuracy of screening and improve the quality of cytopathology test results, it is necessary to perform external quality control.
authors.affiliation: Unit for External Quality Control, School of Pharmacy, Federal University of Goiás, Goiânia, Brazil.
authors.forename: Cinara Zago Silveira
authors.initials: CZ
authors.lastname: Azara
authors.forename: Edna Joana Cláudio
authors.initials: EJ
authors.lastname: Manrique
authors.forename: Nádja Lindany
authors.initials: NL
authors.lastname: Alves de Souza
authors.forename: Andryne Rego
authors.initials: AR
authors.lastname: Rodrigues
authors.forename: Suelene Brito do Nascimento
authors.initials: SB
authors.lastname: Tavares
authors.forename: Rita Goreti
authors.initials: RG
authors.lastname: Amaral
mesh_terms: D001938:Brazil; D005188:False Negative Reactions; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008403:Mass Screening / Q000379:methods / Q000592:standards; D065006:Papanicolaou Test / Q000592:standards*; D010338:Pathology, Clinical / Q000592:standards*; D011786:Quality Control; D015203:Reproducibility of Results; D002583:Uterine Cervical Neoplasms / Q000175:diagnosis* / Q000517:prevention & control; D014626:Vaginal Smears / Q000592:standards*